Teacher killer seeks sentencing mercy

A man who admitted murdering a teacher and setting his house alight has asked the South Australian Supreme Court to impose a non-parole term lower than the mandatory minimum of 20 years.

Shane Troy Clark, 41, stabbed Hamilton Wiseman, 61, five times in the bedroom of his home at Marino in southern Adelaide in April last year.

He then set the house on fire.

Clark pleaded guilty to murder and arson.

The court was told Clark previously had a relationship with Mr Wiseman's step-daughter and the relationship breakdown may in part have triggered his offending.

In victim impact statements, friends and relatives of the dead man described Clark as a monster and a pathetic excuse for a human being.

The victim's wife Leonie said the killing had taken away everything from the family.

"Before the crime, generally we had a very happy life. Life had its problems but we were a strong unit," she said.

"It was the best part of my day to come home to Ham (Mr Wiseman) and the house I loved. Now it is all gone. I was in shock for many weeks. It was hard to accept that Ham, my husband, wasn't here. I knew him for 15 years and we were married for 10.

"Grief does terrible things. It has fractured the family and hurt me terribly. Shane, I am deeply hurt by what you have done. At times, Shane, I have felt compassion towards you. I accepted you into my home ... my daughter gave you all she had. To murder Ham in his sleep was cowardly."

'Difficult to forgive'

The dead man's step-daughter Sheree Muir said her mother's grief added to her own pain.

"Shane, I'm still finding it difficult to forgive you but I hope I will," she told the court.

"The pain and suffering you have caused has not ended. Watching my mother suffering has added to the trauma.

"It was not enough that you killed Ham ... after the fire we were left with just the clothes we were wearing. This is unspeakable, cold-blooded and nasty behaviour. It is not OK to take another human's right to live."

The victim's daughter Bronte spoke of the hatred she now felt.

"Now that he is gone I've lost a part of myself. There is a hole in my heart that will never be repaired," she said.

"I have never felt so much hatred and anger towards a human being. The emotional and psychological impact this has brought me is like nothing I have ever had to endure or experience. I worry that if the accused is ever to walk free, he will ruin the lives of other innocent people."

A friend of the victim, Ashleigh Starke, echoed the anger outside the court.

"Someone like that, you know, I don't believe in an eye for an eye but a vicious dog, what do you do with it?"

Unresolved anger

Defence lawyer Graham Lang asked the court to impose a non-parole period lower than the mandatory minimum because of his client's guilty plea and cooperation with police.

He admitted Clark had unresolved anger.

"I submit from the bar table that he is tortured by what he has done and has to live with it," he told the hearing.

"He does not remember forming the intention to kill but my client has always wanted to take responsibility for his physical actions. To describe it as a significant act of violence is an understatement.

"The separation ... may have triggered this episode but that's not to blame anyone devastated by this tragedy for what happened, he takes full responsibility. He has some recall of stabbing Mr Wiseman but can't recall what he was thinking or feeling at the time."

But prosecutors said Clark only admitted his crimes in the face of an overwhelming case against him.

Prosecutor Sandi McDonald said Clark had told a taxi driver who took him from the casino to Mr Wiseman's home that he was going to kill four people that night.

She said Clark repeatedly told police soon after his arrest that had the rest of the family been there he would have killed them too.